The performance of the thermoelectric materials is represented by the equation of Z=Q^2/rhokappa, where Q is thermoelectric power, rho is electrical resistivity, and kappa is thermal conductivity.The results obtained are as follows :1) Dispersion of epsilon-phase and ZrSi (metallic phase) or SiC (insulator) by mechanical alloying (MA) improved the thermoelectric properties of beta-FeSi_2. It was found that the dispersion of SiC particles decreased the grain size of beta-FeSi_2 and thermal conductivity, kappa, and the dispersion of metallic phases decreased the electrical resistivity, rho.2) beta-FeSi_2 with dispersion of fine SiC particles (20-30nm) was obtained by MA of FeSi_2 with Si and carbon particles. Dispersion of SiC fine particles increased the performance of beta-FeSi_2 by decreasing thermal conductivity kappa without changes in thermoelectric power Q and electrical resistivity rho.3) Addition of Zr significantly increased the themoelectrical performance of beta-FeSi_2 by decreasing the electrical resistivity especially at high temperatures.